Exhaust emission control system

An exhaust emission control system for a vehicle including a primary engine (5) and a secondary engine (6) having a displacement smaller than that of the primary engine is provided with an exhaust passage (250, 260, 262) having a junction portion (264) at which exhaust gas discharged from the primary engine (5) and exhaust gas discharged from the secondary engine (6) join together, and an exhaust emission purifying device (4) that purifies the exhaust gas joined at the junction portion (264) in the exhaust passage (250, 260, 262).